Color filters are made from materials (e.g., dyes) that allow certain wavelengths of light to pass while blocking other wavelengths of light. For example, a red color filter transmits red light, but blocks other wavelengths of light from passing through. Similarly, a green color filter transmits green light, but blocks other wavelengths of light from passing through. Similarly, a blue color filter transmits blue light, but blocks other wavelengths of light from passing through. As can be appreciated, color filters are important components in realizing color sensors.
FIG. 1 illustrates a prior art method for applying a color filter to a sensor chip to manufacture a corresponding color sensor. First, a layer of red color filter material  4 is applied to the microchip 2 through a photolithographic process, for example. The red filter material coats the microchip 2. Next, portions of the red color filter material that are not needed are removed. What remains is a red color filter 6 that is disposed over the portions of the microchip 2 (e.g., over a sensor area). In this example, a red filter material 4 is applied to the microchip 2. To implement a green sensor, a green filter material is applied to a corresponding sensor. Similarly, to implement a blue sensor, a blue filter material is applied to a corresponding sensor. In this manner, red sensor, a green sensor, and a blue sensor can be manufactured.
As can be appreciated, the above process limits the materials that can be used to realize red sensors, a green sensors, and a blue sensors. Another significant disadvantage of this processing technique for realizing color filters is that the transmittance of other undesired wavelengths are not eliminated. For example, some wavelengths in the infra-red region and the ultra-violet region are not blocked and pass through the prior art color filter implementations. FIG. 1 further illustrates an exemplary transmittance versus wavelength plot 8 for the prior art color sensor and an ideal transmittance versus wavelength plot 9. It is noted that the ideal transmittance versus wavelength plot blocks all wavelengths except the desired wavelength (e.g., wavelength corresponding to red, wavelength corresponding to green, or wavelength corresponding to blue). However, the transmittance versus wavelength plot of the prior art color filter indicates a relatively high transmittance at P1 and P2, which is not desirable.
Another problem with color sensors that is not related to color filters is the dependence on operating temperature. The performance of the sensor and in particular the output voltage generated by the sensor depends on the operating temperature of the color sensor. These differences in output voltage are referred to as offset voltages or leakage current. Prior art color filter implementations do not address or mitigate this problem.
Based on the foregoing, there remains a need for a color filter method and apparatus that that overcomes the disadvantages set forth previously.